Unveiling the local deformation behavior of typical microstructures of nickel-based single crystals under nanoindentation

In the present study, consider the typical microstructures (γ, γ’ and interface phases) in nickel-based single crystal, three ideal simplified atomic models of Ni, Ni₃Al and Ni/Ni₃Al interface were established. And nanoindentation molecular dynamics (MD) simulations were performed on the above models. Based on the dynamic deformation behavior and mechanism of nickel-based single crystal microstructure under the local loading, the nanoindentation plastic deformation is divided into two stages P_i and P_ii. In the initial P_i stage, dislocations only move and react on the contact surface between the indenter and the substrate. Subsequently, in stage P_ii, edge dislocations climb away from the contact surface, screw dislocations interact with each other and finally form dislocation shear loops. The local plastic deformation is dominated by the nucleation and emission of dislocation loops, affected by its resistance and dislocation velocity. It is noted that in the interface model, dislocation shear loops inevitably interact with interface dislocations, which will lead to further plastic deformation. Combined with the dislocation theory and the above research, a model based on the movement of dislocations was established better describe the local plastic behavior of the typical microstructure in nickel-based single crystal under indentation.